The present invention relates to a method and circuit of measuring and displaying physical values, preferably low temperatures and low pressures, with the aid of a sensor furnishing voltage signals, in which a signal furnished by the sensor is compared, with the aid of electronic means, with the known sensor characteristic which has been stored in these electronic means and a display signal is formed on the basis of this comparison.
It is known to measure physical values with the aid of sensors which produce a voltage signal corresponding to the value being measured. In this connection, the problem frequently arises that the sensor characteristic is not linear, i.e. that a linear dependency does not exist between the signals furnished by the sensor and the values of the physical parameter being measured, which values form the basis of the sensor signals.
Known sensors, in particular for measuring low temperatures and low pressures, have relatively complicated characteristics. For example, sensors employed for such measurements--preferably for temperature measurements--are silicon diodes, resistors made of carbon, Ge or Pt, thermistors or thermocouples.
In a known method of the above-mentioned type for measuring and displaying low temperatures an Si diode serves as the sensor. Its measurement signals are fed to a microprocessor by way of an analog/digital converter. The microprocessor is programmed with a computer program and is also fed the sensor characteristic. This arrangement makes it possible to compute and display the associated temperature value for every measurement signal value. The drawback of this type of measurement value processing is the need to use relatively expensive components, particularly a microprocessor. Moreover, the setting up of the required computer programs, loading these programs into the microprocessor and storage of the sensor characteristic involve relatively high expenditures which contribute to the costs of measuring devices of this type. A further drawback is that a change in the type of sensor requires a change in the microprocessor or at least an expensive change in microprocessor software.